1. Field of the Invention
This invention relates generally to a magnetic recording head used in a disk drive, and more particularly to a magnetic recording head incorporating a heat sink.
2. Description of the Background Art
Disk drives using magnetic recording of digital information store most of the information in contemporary computer systems. A disk drive has at least one rotating disk with discrete concentric tracks of data. Each disk drive also has at least one recording head typically having a separate write element and read element for writing and reading the data on the tracks. The recording head is constructed on a slider and the slider is attached to a suspension. The combination of the recording head, slider, and suspension is called a head gimbal assembly. In addition, there is an actuator which positions the recording head over the specific track of interest. The actuator first rotates to seek the track of interest and after positioning the recording head over the track, maintains the recording head in close registration to that track. The disk in a disk drive has a substrate and a magnetic layer on the substrate for magnetic recording. The slider carrying the recording head has a disk facing surface upon which an air bearing is constructed. The air bearing allows the slider to float on a cushion of air and to be positioned close to the disk surface. Alternatively, the slider surface facing the disk can be adapted for partial or continuous contact with the disk.
The recording head is formed from various metals and is separated from the body of the slider by a thin insulating layer. The value of the coefficient of thermal expansion of the materials in the recording head is generally higher than the corresponding value for the insulating layer or the slider. Therefore as the temperature of the recording head and slider is increased, the physical expansion is greater for the recording head than for the insulating layer or the slider. The rise in temperature is most noticeable during writing when write current is passed through the write element of the recording head. During writing, heat is generated in the coils by Joule heating, and in the magnetic portion of the yoke by Eddy current heating. Upon heating, the recording head may protrude several nanometers out of the air bearing surface of the slider toward the disk because of the mismatch in thermal expansion coefficients and higher temperature in the region close to the coil compared with the slider body.
The flying height of the slider above the disk surface is generally lower for each new family of disk drive products to facilitate achieving ever higher densities of recorded information. The required flying heights are now comparable with the amount of recording head protrusion caused by temperature increases during writing. Contact between the recording head and the disk can cause damage to the recording head and can also lead to wear failure at the interface between the recording head and the disk.
The alternate contact recording apparatus allows contact between the slider and the disk. However, while a slider surface may be constructed to allow partial or continuous contact with the disk, a recording head which protrudes from the disk facing surface of a slider is subject to excessive wear damage.
Thus, the mismatch between the thermal expansion coefficients of the recording head and the slider leading to protrusion of the recording head is an increasingly serious problem.